1. Field of the Invention
The present invention relates to a hybrid lens and a hybrid lens forming method in which an aspherical composite layer is made of an ultraviolet-curing resin. More particularly, the present invention relates to a hybrid lens forming method in which a forming die for forming an aspherical composite layer transmits ultraviolet rays, and a precise aspherical composite layer is formed, without any influence of the curved surface of the lens or the like, by applying ultraviolet rays to a resin from the side of the forming die and thereby curing the resin.
2. Description of the Related Art
Conventionally, so-called hybrid lenses, in which an aspherical composite layer is formed on a single lens of optical glass serving as a parent material, are commercially practical as a means for forming an aspherical lens at relatively low cost. The hybrid lenses are produced by transferring an aspherical composite layer made of an ultraviolet-curing resin to the lens surface of a single lens made of optical glass.
FIG. 13 shows a conventional hybrid lens forming method. In this method, after a predetermined amount of ultraviolet-curing resin 32 is poured on a mirror-finished transfer face 31 of a die 30 for forming an aspherical composite layer, a convex lens 33 is placed in the die 30 and fixed thereto by using a support frame 34. The ultraviolet-curing resin 32 thereby fills the entirety of the transfer face 31. When ultraviolet rays UV are applied from the side of the convex lens 33 for a predetermined time in this state, the ultraviolet-curing resin 32 is cured with the ultraviolet rays transmitted through the convex lens 33, and a hybrid lens is formed with an aspherical composite layer transferred to the convex lens 33.
The above-described method allows a precise hybrid lens to be produced at a relatively low cost because the die 30 is excellent in workability and durability. However, since the convex lens 33 sometimes does not transmit ultraviolet rays well depending on the type of the optical glass, an excessively long time is needed to cure the ultraviolet resin 32 and productivity is thereby reduced. For this reason, the types of available optical glasses are limited, and this decreases the degree of freedom in design.
Since the ultraviolet-curing resin 32 is cured with the ultraviolet rays UV which are applied from the side of the convex lens 33 and are transmitted therethrough, the ultraviolet rays UV are prone to be influenced by the lens curvature. For example, since the convex lens 33 has a light collecting function, the applied ultraviolet rays UV concentrate in the center of the convex lens 33, as shown in FIG. 13, and the intensity distribution thereof is nonuniform. For this reason, the ultraviolet-curing resin 32 is not cured uniformly, and it is difficult to produce a precise hybrid lens.
The present invention has been made in order to overcome the above problems, and an object of the invention is to provide a hybrid lens and a hybrid lens forming method in which a precise hybrid lens can be produced by effectively and uniformly curing an ultraviolet-curing resin without being affected by the type of optical glass and the curvature.
In order to achieve the above object, according to an aspect of the present invention, there is provided a hybrid lens forming method in which a forming die is made of a material which transmits light rays, and a composite layer is transferred onto a lens by applying light rays from the side of the forming die and curing a photocurable resin with the light rays transmitted through the forming die.
According to the above-described hybrid lens forming method, since the photocurable resin can be cured with the light rays applied from the side of the forming die, the light rays are not affected by the lens curvature, and the photocurable resin can be irradiated with a uniform intensity distribution. This makes it possible to produce a precise hybrid lens without causing nonuniform curing of the photocurable resin.
According to another aspect of the present invention, there is provided a hybrid lens in which a lens frame is formed integrally with a composite layer. In this case, it is possible to omit the subsequent step of assembling the lens frame to the hybrid lens, to reduce the number of components, and to reduce the cost of the hybrid lens.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.